Patients suffering from kidney disorders rely on a variety of external blood treatments to remove the harmful waste substances that build up in their blood over time. One of the most common methods of treatment is hemodialysis.
Hemodialysis typically involves two networks of fluid passageways miming adjacent to one another in a counter current flow arrangement. Blood is passed through one set of tubules and a cleaning solution is passed through the other. The pH and osmotic potential of the cleaning solution is adapted such that waste compounds built up in the blood diffuse from the blood into the cleaning solution via a semi permeable membrane which separates the blood and cleaning solution sides of the network of fluid passageways.
This provides a method of gradually removing waste materials from the blood minimising fatigue to the patient. However, there are some disadvantages associated with hemodialysis not present with other forms of blood treatment.
Many mid-size and large-size waste solutes dissolved in the blood (including such as proteins and polypeptides) are difficult to remove completely from the blood using diffusion alone and it can take a long time to reduce the levels of these substances in the blood to acceptable levels. An alternative approach is to use hemodiafiltration.
Hemodiafiltration involves administering sterile cleaning solution to the blood either by employing a large hydrostatic potential to force sterile cleaning solution across a semi permeable membrane into the blood or by directly adding it to the blood; and then pulling the sterile cleaning solution, complete with dissolved waste products, back across the semi permeable membrane for subsequent disposal.
Examples of hemodiafiltration machines are disclosed in, for example “Lee, K., et al., Evaluation of a New Method for Pulse Push/Pull Hemodialysis: Comparison with Conventional Hemodialysis, ASAIO Journal, 2012, page 232-237”.
This type of blood treatment is not limited by diffusion as sterile cleaning solution is allowed to mix directly with the blood. However, the rapid extraction of waste products from a patient's blood regularly leaves patients fatigued.
Accordingly, what is required is a device which is able to facilitate both methods of blood treatment during the same treatment session based on the patients specific requirements.